r."

He leaned over the mouth of the shaft and gave a shrill whistle.

In an instant all was silent below.

Half a minute later he repeated the whistle thrice.

There was a clatter below of arms and accoutrements.

"Over behind those big cactus with you, quick," was the next
command. "If you insist on fighting these men later, you can.
Now let's get rid of them."

For just a moment the boys hesitated, but there was something in
the man's manner that seemed to force obedience and they obeyed.

They were not a moment too soon, for they had no more than
secreted themselves than the back wall of the ruin flew open and
the men rode out. Of those who had been at the mouth of the shaft
only a few moments before, only the mountebank with his ape was
in sight.

"What is it?" asked one of the band, riding up to him.

"Guard the track at the summit. Let no train pass, even if you
have to tear up the track."

"By whose order?"

The mountebank made a mysterious sign with his left hand.

"_Bueno!_" from the horseman. "Close up the doors and care for
the wounded," and putting spurs to his horse, he led the bandits
from the basin.

As soon as they were out of sight, the mountebank summoned the
boys to the shaft house by a wave of his hand.

"Now," he said, "you'll have a chance to test your nerve, and we
must work rapidly to get where we wish to go before dark."

He took from a crude knapsack which he wore upon his shoulders a
coil of cord about half the size of a lead pencil, but evidently
of much strength. Then seizing the ape, he fastened one end of
the cord to the belt about the animal's body, and despite its
unwillingness to be thus treated began to lower it into the
shaft.

Totally unable to account for his actions, the boys stood
speechless, watching the operations.

After some minutes, the cord slackened.

"He's reached the bottom," was the information vouchsafed. Then a
moment later: "Help me to pull him up, one of you."

Billie hastened to lend a hand and in a short time the head of
the ape appeared above the edge of the shaft. In his hand he held
one end of a good-sized rope, which the mountebank took and tied
around one of the stone pillars which supported the roof.

"Now, then," he said, "we are ready to descend into the old mine.
Which one of you will go first?"

The boys looked at each other, but there was no reply until
Donald asked:

"Why should we go down at all?"

"Why," was the somew